The present invention relates in general to airport beacons which produce a bright signal as a visual aid for airplane pilots in locating airports during night flights, etc. In particular, the present invention relates to an airport beacon having a rotatable lens assembly.
Airport beacons produce and sweep a bright light through a complete 360 degree revolution as an aid to aerial navigation. Historically, airport beacons have used high powered incandescent lamps having a relatively short life. In order to decrease the inconvenience and costs of frequent bulb changes, automated bulb changer assemblies were mounted within and rotated with a lens assembly. In these arrangements, slip rings were used to carry power up to the rotating lamp, and various other components such as transformers and capacitors were mounted within and rotated with the lens and lamp assembly so that only a low voltage had to be applied across the slip rings.
Slip rings are still in use today as evidenced by U.S. Pat. No. 4,717,991 to Murphree, Jr. which discloses a metal halide lamp which rotates simultaneously with a lamp housing having a color coded lens assembly. A transformer, capacitor and photoelectric switch are mounted under a heat shield and also rotated with the housing and lamp.
Due to the inconvenience and expense of maintaining airport beacons, low maintenance components are desired. Slip rings are a high maintenance component which must be cleaned regularly to remove carbon and possible grease and dirt build-up on the rings and brushes.
Another high maintenance component of the present airport beacon lights is the worm gear drive system currently used to drive the lens and lamp assembly. The worm gear drive system has a relatively short life and must be greased at least twice a year in order to maintain adequate performance.